Mathematical operators and symbols support

Modern markup languages such as MathML, or programming languages such as Agda, Haskell and Scala can make extensive use of the Greek alphabet and mathematical symbols. Users of these languages could benefit from **Source Code Pro** if these characters were supported. In particular Agda and MathML make the most extensive use of Unicode, by design.

Issue #48 already requests Greek alphabet support.

Here are some quite comprehensive list of mathematical symbols:
- **MathML 2.0: Characters, Entities and Fonts** (W3C): http://www.w3.org/TR/MathML2/chapter6.html
- **Unicode Entity Codes for Math** (PSU): http://archive.tlt.psu.edu/suggestions/international/bylanguage/mathchart.html
- **Mathematical operators and symbols in Unicode** (Wikipedia): http://en.wikipedia.org/wiki/Mathematical_operators_and_symbols_in_Unicode

Here are some code snippets and blog posts making use of this feature:
- http://www.w3.org/TR/MathML2/chapter6.html
- http://code.haskell.org/Agda/examples/SimpleTypes.agda
- http://code.haskell.org/Agda/examples/Introduction/Unicode.agda
- http://scalaz.github.com/scalaz/scalaz-2.9.0-1-6.0.1/doc.sxr/scalaz/MA.scala.html
- http://conal.net/blog/posts/a-third-view-on-trees